In the electronics industry, a continuing objective is to further and further reduce the size of electronic devices while simultaneously increasing performance and speed. Cellular telephones, personal data devices, notebook computers, camcorders, and digital cameras are but a few of the consumer products that require and benefit from this ongoing miniaturization of sophisticated electronics.
Integrated circuit (“IC”) assemblies for such complex electronic systems typically have a large number of interconnected IC chips. The IC chips are usually made from a semiconductor material such as silicon or gallium arsenide. Photolithographic techniques are used to form the various semiconductor devices in multiple layers on the IC chips.
Heat management through such a structure can be critical. The internal thermal resistance and thermal performance of the flip chip interconnect technology are determined by a series of heat flow paths. By making high heat conductivity connections between the bottom of the die and the substrate, heat generated in the die can be transferred efficiently from the die to the substrate.
For applications where additional heat must be removed from the semiconductor die, the molding compound that encapsulates the die can be partially omitted from the upper surface of the die to partially expose this surface. The exposed die surface can then be put in direct physical contact with a heat spreader that overlies the semiconductor die. To enhance the cooling performance, a layer of thermal grease or the like can be spread between the die surface and the heat spreader to improve heat transfer to the heat spreader.
The heat spreader is typically formed so that it can also be attached to the underlying substrate, resulting in a mechanically strong package. Where necessary, the heat spreader can also be encapsulated in a molding compound that is formed overlying the upper surface of the package.
The heat thus flows first from the semiconductor device to the body of the semiconductor module or package into which it has been incorporated, and then to the package surface and to the heat spreader that is attached to the package surface. Unfortunately, there are drawbacks associated with the use of known heat spreaders and other semiconductor packages. Among these drawbacks are heat spreader manufacturing costs, complicated assembly processes, and concerns about package reliability.
Modern electronic systems demand continued decreases in size. The volumetric size of systems is dependent not only on the area of the semiconductor package, but also on the thickness of the semiconductor package. Using thin semiconductor packages allows smaller electronic systems to be built. Current trends place a premium on semiconductor packages that can incorporate multiple semiconductor dies in stacks or stacks of packages.
One proposed solution involves providing a heat sink or metal slug attached to the semiconductor package to help remove the heat. Unfortunately, this additional heat sink or metal slug adds to the package thickness, and prevents stacking of multiple packages.
Another proposed solution involves mounting the semiconductor die within an interior metal housing having sidewalls and flanges for retention. Unfortunately, this creates the need to use longer bond wires. Additionally, added vertical stress is created by the metal sidewalls of the housing.
Thus, a need still remains for thin packages with high thermal dissipation and it is increasingly critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.